[llvm-dev] Understanding targets

[Daniel Sanders via llvm-dev]

> On Nov 13, 2019, at 07:48, Simon Atanasyan via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> On Wed, Nov 13, 2019 at 6:28 PM Robinson, Paul <paul.robinson at sony.com> wrote:
>> 
>> Regarding the Mips target, it looks like the supported 32-bit architecture
>> names are “mips” and “mipsel” so you could experiment with using triples
>> starting with those strings.  I don’t know anything in particular about
>> the Mips target other than what I just said.  I have cc’d the code owner
>> of the MIPS target, who might be able to help you there.
> 
>>> I see there “Mips” and “RISCV” but no RISC MIPS or even a R3000 – does that
>>> now mean that Clang does not support does old processors? Or does it? What
>>> do I do if I encounter a ‘wild’ Clang without llvm-config – can I still find
>>> out its targets? I have no idea and this is why I’m asking.
> 
> Now Clang accepts the following MIPS CPU names. This list can be found
> in the "clang/lib/Basic/Targets/Mips.cpp". mips1 and mips5 accepted by
> Clang, but unsupported by code generator. I'm going to remove them
> from this list.
> 
> mips1, mips2, mips3, mips4, mips5,
> mips32, mips32r2, mips32r3, mips32r5, mips32r6,
> mips64, mips64r2, mips64r3, mips64r5, mips64r6,
> octeon, octeon+, p5600
> 
> R3000 is a CPU implements mips1 instruction set architecture.
> Unfortunately you cannot generate a code for this CPU using Clang.

We never implemented mips1 codegen as it was orders of magnitude harder than mips2 (mostly because of the delay slots on load instructions) and there's no 'generic' mips1 target (because coprocessor 0 wasn't standardized).
However, we had mips2 working as it was needed to build for Debian. Did it get broken or did they move their mips port up to something more recent?
I think David is actively using mips4 too. @David: Is that right?

> -- 
> Simon Atanasyan
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